Space shuttle Atlantis landing

SCOTT AUDETTE, REUTERS

The crew of space shuttle Atlantis stands at left as NASA Administrator Charles Bolden (R) speaks after landing at the Kennedy Space Center in Cape Canaveral, Florida, July 21, 2011. The 12-day mission to the International Space Station completes the last mission in the Space Shuttle Program. From left are Mission Specialist Rex Waldheim, Mission Specialist Sandra Magnus, Pilot Doug Hurley and Mission Commander Chris Ferguson.

The crew of space shuttle Atlantis stands at left as NASA Administrator Charles Bolden (R) speaks after landing at the Kennedy Space Center in Cape Canaveral, Florida, July 21, 2011. The 12-day mission to the International Space Station completes the last mission in the Space Shuttle Program. From left are Mission Specialist Rex Waldheim, Mission Specialist Sandra Magnus, Pilot Doug Hurley and Mission Commander Chris Ferguson. (SCOTT AUDETTE, REUTERS)

The crew of space shuttle Atlantis stands at left as NASA Administrator Charles Bolden (R) speaks after landing at the Kennedy Space Center in Cape Canaveral, Florida, July 21, 2011. The 12-day mission to the International Space Station completes the last mission in the Space Shuttle Program. From left are Mission Specialist Rex Waldheim, Mission Specialist Sandra Magnus, Pilot Doug Hurley and Mission Commander Chris Ferguson.